Photovoltaic cells convert sunlight into electricity providing an alternative energy source. High costs of silicon based solar panels and difficulties associated with manufacturing such panels limit commercial success of this technology. Organic photovoltaic cells by comparison offer advantages with respect to economical cost, weight and flexibility.
The organic photovoltaic cells operate by light being absorbed at an active layer of the cell that includes molecules or compound moieties that define donors and acceptors. When photons are absorbed, photo-induced electron transfers take place from the donors to the acceptors leading to electron-hole pairs that can be harnessed to generate the electricity. However, proximity of the donors to the acceptors influences this charge transfer in a manner that limits conversion efficiencies obtainable with prior devices.
In past approaches to provide the active layer, blends of polymeric donor compounds and fullerene acceptor compounds tend to phase segregate during manufacturing of the photovoltaic cells preventing desirable intimate mixing thereof. Further, dyad compounds that include both acceptor moieties and donor moieties tend to lack sufficient separation thereof to prevent unwanted recombination of electrons and holes within the active layer. Complexity in synthesis of such dyads also contributes to expense of the cell.
Therefore, a need exists for compounds and their use in a photoactive layer to produce solar panels having beneficial attributes.